Field tests of low noise levels from MVHR ventilation systems – Overview obstacles and pilot test of test procedure improvement

The Danish building regulations specify LAeq ≤ 30 dB for ventilation noise in dwellings, both for new-build and new systems in renovated housing. The test method referred to is based on the survey method ISO 10052.
In practice, many people get annoyed or disturbed by ventilation noise during night or when having quiet activities. Several people complain about the noise, and some people change the operation of the MVHR system or even destroy it. Due to dissatisfaction from occupants, it is considered reducing the regulatory limit to LAeq ≤ 25 dB in living and sleeping rooms, which is currently being tested in a voluntary sustainability class (in Danish abbreviated FBK), including use of the engineering method ISO 16032 for background noise correction as prescribed in the FBK guidelines.
However, even with a background noise correction specified, for both limits LAeq ≤ 30 dB and LAeq ≤ 25 dB, it’s often a challenge to quantify the background noise from various activities or traffic noise in the rooms to be tested. For that main reason, amended test procedures compensating for the shortcomings of the basic test procedures are needed. One potential tool might be increasing temporarily the airflow during test, implying much higher noise levels and thus less sensitivity to background noise, and then subsequently adjust the noise level to fit the nominal air flow, before reporting.
The paper describes test results from a preliminary field test with increased air flow, summarizes conclusions and indicates suggestions for a wider, future field study.